Stacked plate heat exchangers typically comprise a plurality of plate pairs stacked one on top of the other with each plate pair having opposed inlet and outlet openings such that when the plate pairs are stacked together, the inlet and outlet openings align to form inlet and outlet manifolds and thereby establish communication between fluid channels formed inside each plate pair. The plate pairs are usually joined together by brazing. However, as the plate pairs tend to be unsupported in the area of the manifolds, the heat exchanger in the area of the inlet and outlet openings tends to distort under the pressure of the fluid flowing therethrough and will often expand like an accordion or “bellows” in the manifold region. The distortion that occurs in the manifold regions of the heat exchanger tends to lead to premature failure or cracking and leaking in the heat exchanger.
One approach used to reinforce the inlet and outlet areas of a heat exchanger is to use exterior clamps or brackets that are brazed to the outside of the heat exchanger to keep it from expanding under pressure. Another approach is to insert perforated or slotted tubes through all of the aligned inlet and outlet openings of each plate, the tubes being brazed to the peripheries of the respective inlet and outlet openings. Yet another common approach is to use a large area washer or reinforcing plate to space the plate pairs apart and to create the fluid communication between the fluid channels formed by the plate pairs. The additional surface area provided by the large area washer or reinforcing plate provides additional support to the typically unsupported area between plate pairs; however, these types of washers can be costly and therefore increase overall manufacturing costs associated with the particular heat exchanger.
U.S. Pat. No. 5,794,691 (Evans et al.) discloses a heat exchanger made from a plurality of stacked plate pairs wherein the inlet and outlet openings that form the manifolds include opposed flange segments formed on the inner peripheral edges of the openings. The flange segments extend inwardly and are joined together when the plates are stacked together to prevent expansion of the manifolds when under pressure.